This present invention relates to a displacement bearing with at least two rollerbodies guilding an inner part there between, and a motorcycle fork with the displacement bearing.
DE 199 57 964 A1 has disclosed a front wheel guide for a motorcycle. The motorcycle has a motorcycle fork with two forked pipes. Each forked pipe consists of a bottom part, which may be referred to as the “wheel carrier pipe” and on which the front wheel is mounted. The wheel carrier pipe forms an outside part of a displacement bearing. A banana-shaped inside part is inserted into the wheel carrier pipe, forming the lower section of an upper forked pipe element. The banana-shaped end piece of the upper forked pipe has one guide face on its front end and another on its rear end. Roller bearings which can roll on the guide surfaces are provided in the wheel carrier pipe. The banana-shaped end piece can be displaced in relation to the wheel carrier, with the roller bearings and/or roller bodies rolling on the guides. Details regarding the specific design of the guide faces and the roller bearings and/or roller bodies are not included in DE 199 57 964 A1.
The object of this invention is to improve upon the bearing described above so that it will be permanently without play.
This invention is based on a displacement bearing having an inside part and an outside part. The inside part has raceways on its inside extending in the direction of displacement. The outside part extends around the inside part and is displaceable in relation to the inside part. At least two roller bodies are provided in the interior of the outside part. The roller bodies are mounted to rotate about an axis of rotation arranged in the interior of the outside part. With a displacement of the inside part in relation to the outside part, the roller bodies roll on the raceways of the inside part.
The basic principle of this invention consists of using roller bodies having a convex shape and designing the raceways on which the roller bodies roll with a concave shape. Due to the convex shape of the roller bodies and the concave shape of the raceways, the displacement bearing can absorb compressive forces acting perpendicular to the raceway as well as lateral forces acting across the raceway. The roller bodies are in close contact with the raceways, which ensures a good distribution of forces and prevents material from flaking off.
According to one embodiment of this invention, the axes of rotation of the roller bodies—comparable to a chord of an arc of a circle—cover an arc-like segment of the wall of the outside part. The ends of the axes of rotation are attached to and/or mounted on the inside of the outside part.
The roller bodies may be designed to be spherical or ellipsoidal or with a cambered shaped in general. The roller bodies are preferably designed so they are flattened at the sides. In the case of spherical roller bodies, these are then “flattened” spheres, i.e., spherical bodies on which the dome-shaped sections on the sides are “missing.”
The outside part is preferably a closed pipe, e.g., a cylindrical pipe and/or a bearing cage in the form of a cylinder. The outside part preferably has wall sections that are distributed over its circumference and differ in wall thickness. The rigidity of the outside part can be specified through the design with a wall thickness that varies over the outside circumference. A very important quality criterion of displacement bearings is that they are without play. Absence of play should be ensured over the entire lifetime of the bearing if possible. Freedom from play can be achieved by “prestressing” the roller bodies with respect to the raceways and/or the inside part. The roller bodies are mounted in the outside part and are themselves virtually inelastic. Therefore the outside part must have a certain radial elasticity at least in the area of the roller bodies. The required elasticity can be achieved through suitable dimensioning of the wall thickness of the outside part in the individual circumferential areas. The wall thickness of the outside part in the wall sections covered by the axes of rotation and the roller bodies is preferably lower than that in the other wall section. Thus the outside part can turn radially to a certain extent in the area of the roller bodies.
The outside part is preferably a cylindrical bearing ring. With this motorcycle fork, this bearing ring is secured in the wheel carrier pipe by pressing, for example. Pressing results in forces acting radially from the outside on the bearing ring. Nevertheless, as explained above, the outside part, i.e., the “bearing ring” must have a certain radial elasticity, at least in the area of the roller bodies. Therefore, a recess is preferably provided on the outside of the outside part in the wall sections of the outside part covered by the axes of rotation and the roller bodies. In the area of the wall sections of the outside part covered by the roller bodies and the axes of rotation, there is thus a certain radial clearance between the outside circumference of the outside part and a component surrounding the outside part, e.g., a wheel pipe carrier into which the outside part is pressed. This clearance permits a certain radial expansion of the outside part.
In addition, it is possible for the wall of the outside part to have a feed-through opening in the central area of the axes of rotation. With such a feed-through opening, it is possible to achieve a weakening of the material of the wall of the outside part and thus to achieve the required elasticity. In addition, a feed-through opening has the advantage that the roller bodies can approach closer to the outside circumference of the outside part. Part of the roller bodies may even protrude into the feed-through opening, i.e., into the wall area of the outside part, which permits a very compact design.
The roller bodies may be supported with friction bearings or roller bearings on the axes of rotation. The displacement bearing may have two or more roller bodies. If two roller bodies are provided, they may be arranged in diametrically opposite positions in the outside part.
In addition, in the central area of the respective axis of rotation, it is possible for the roller bodies to have a “follower element” in their outside circumference. The follower element may be, for example, an elastic plastic ring or gearing. It ensures that the roller bodies will in fact roll on the raceways when there is a relative displacement of the inside part with respect to the outside part. Sliding friction can thus be prevented.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.